Japanese patent application publication no. 2000-245975A discloses a conventional wall climbing toy. As shown in FIGS. 1 to 3, the conventional wall climbing toy includes a main body 90, a motor (M) mounted inside the main body 90, an upper shaft 91 coupled to be driven by the motor (M) to rotate, a lower shaft 92 coupled to be driven by the motor (M) to rotate, an upper crank member 93 coupled to the upper shaft 91 to rotate therewith, a lower crank member 94 coupled to the lower shaft 92 to rotate therewith, front and rear bellows pumps 95, 96, a frame body 97 mounted on a lower surface of the main body 90, four suction cups 98, 99 attached to the frame body 97, and four air tubes (P) each connecting an interior cavity of a corresponding one the suction cups 98, 99 to a corresponding one of the front and rear bellows pumps 95, 96.
The front and rear bellows pumps 95, 96 are mounted on a slider 900. The slider 900 is slidably mounted on the main body 900 and has a slot 900a. The upper crank member 93 has a connection pin 931 which is disposed radially offset from a rotation axis of the upper shaft 91 and which is slidably engaged in the slot 900a. Each of the front and rear bellows pumps 95, 96 is convertible between a collapsed state and an extension state. When the upper shaft 91 is rotated to permit the upper crank member 93 to rotate therewith, the front and rear bellows pumps 95, 96 are alternately converted from the extension state to the collapsed state. When the front bellows pump 95 is converted from the collapsed state to the extension state, the suction cups 98 can be deformed to form an air seal with a flat surface (not shown). When the front bellows pump 95 is converted from the extension state to the collapsed state, the air seal is broken to permit the suction cups 98 to leave the flat surface. Similarly, when the rear bellows pump 96 is converted from the collapsed state to the extension state, the suction cups 99 can be deformed to form an air seal with the flat surface. When the rear bellows pump 96 is converted from the extension state to the collapsed state, the air seal is broken to permit the suction cups 99 to leave the flat surface.
The frame body 97 includes a front segment 971 and a rear segment 972. The front segment 971 is pivotably mounted to the main body 90 by means of a front shaft 973, and has an elongated slot 974. The rear segment 972 is pivotably mounted to the main body 90 by means of a rear shaft 975 and has a protrusion 976 slidably engaged in the elongated slot 974.
The lower crank member 94 has a connection pin 941 which is disposed radially offset from a rotation axis of the lower shaft 92, and which is slidably coupled to the front segment 971. When the lower shaft 92 is driven to rotate, the front and rear segment 971, 972 are swung about the front and rear shafts 973, 975, respectively. When the front segment 971 is swung in a clockwise direction, the rear segment 972 is swung in a counterclockwise direction, and when the front segment 971 is swung in a counterclockwise direction, the rear segment 972 is swung in a clockwise direction. During operation, the upper shaft 91 and the lower shaft 92 are driven to rotate simultaneously, the front and rear segments 971, 972 are swung relative to each other, and the suction cups 98 and the suction cups 99 are alternately converted from the extension state to the collapsed state. Thus, the conventional wall climbing toy can move on a wall.